1. Field of the Invention
The present invention relates to a USB function apparatus, and in particular, to a USB function apparatus which supports a plurality of USB descriptors.
2. Description of the Related Art
A USB function apparatus has been proposed which supports a plurality of USB descriptors corresponding to a plurality of functions. With this apparatus, if a user selects one of the plurality of functions, the USB descriptor corresponding to the function selected by the user is transmitted to a USB host apparatus (see Japanese Patent Application Publication No. 2001-202325). For example, if a camera (USB function apparatus) has a mass storage class function (which allows the camera to be treated as an external storage device) and a still image class function (that allows the camera to transfer each still image), when the user selects the mass storage class function on the camera, the USB descriptor representing the mass storage class function is transmitted to a personal computer (USB host apparatus) via a USB.
Another USB function apparatus has been proposed with which a USB host apparatus transmits a vendor-unique command to the USB function apparatus to request a descriptor to be switched. Upon receiving the vender-unique command, the USB function apparatus switches the USB descriptor to be transmitted to a USB host to one assumed by the USB host apparatus (see Japanese Patent Application Publication No. 2001-222503). For example, a personal computer (USB host apparatus) is assumed to correspond only to a mass storage class function. A camera (USB function apparatus) connected to the personal computer via a USB is assumed to have the mass storage class function and a still image class function. Then, when the personal computer transmits a vendor-unique command to the camera, the descriptor transmitted by the camera to the personal computer is switched to the USB descriptor representing the mass storage class function.